I second tres leches cake. I love it, but don't see a recipe here. I did find a flan recipe that looks fantastic, and if you wanted, you could sub out the cardmaom (which I don't think is particularly mexican) for a bit of cinnamon and vanilla.

Thank you for the suggestions. I am leaning toward a chocolate ancho chili cupcake with Choc buttercream w/coffee or the chocolate Patron liqueur and I might do the Tres Leches cake and incorporate coconut milk or coconut rum. I may try these out before the party and see what I think.

I second the Mexican Wedding cookies idea! They are delicious and you could mound them up on decorative platters or put them in little baggies as favors.
Also, with the two rich cakes, how about a spicy fruit salad to cut the richness and offer a lighter choice? I had the most wonderful fruit salad with chili powder and lime juice on a recent trip to Mexico, freshly prepared in a cart alongside the road. Here is a recipe: http://vegetarianfoodrecipes.... It would be best with melons, papaya, and mango.